/**
 * 带流动线纹理材质效果的线工具类
 */
export default class PolylineTrailLinkTool {

    constructor(viewer) {
        this.viewer = viewer
    }
    /**
     * 创建材质
     * @param {*} imgUrl 
     */
    createPolylineTrailLinkMaterial(imgUrl) {
        function PolylineTrailLinkMaterialProperty(color, duration, d) {
            this._definitionChanged = new Cesium.Event();
            this._color = undefined;
            this._colorSubscription = undefined;
            this.color = color;
            this.duration = duration || 3000;
            this._time = (new Date()).getTime();
            this._d = d;
            this.isTranslucent = function () {
                return true;
            }
        }

        Object.defineProperties(PolylineTrailLinkMaterialProperty.prototype, {
            isConstant: {
                get: function () {
                    return false;
                }
            },
            definitionChanged: {
                get: function () {
                    return this._definitionChanged;
                }
            },
            color: Cesium.createPropertyDescriptor('color')
        });
        PolylineTrailLinkMaterialProperty.prototype.getType = function (time) {
            return 'PolylineTrailLink';
        }
        PolylineTrailLinkMaterialProperty.prototype.getValue = function (time, result) {
            if (!Cesium.defined(result)) {
                result = {};
            }
            result.color = Cesium.Property.getValueOrClonedDefault(this._color, time, Cesium.Color.WHITE, result.color);
            result.image = Cesium.Material.PolylineTrailLinkImage;
            result.time = (((new Date()).getTime() - this._time) % this.duration) / this.duration * this._d;
            return result;
        }
        PolylineTrailLinkMaterialProperty.prototype.equals = function (other) {
            return this === other ||
                (other instanceof PolylineTrailLinkMaterialProperty &&
                    Property.equals(this._color, other._color))
        }
        Cesium.PolylineTrailLinkMaterialProperty = PolylineTrailLinkMaterialProperty;
        Cesium.Material.PolylineTrailLinkType = 'PolylineTrailLink';
        Cesium.Material.PolylineTrailLinkImage = imgUrl;
        Cesium.Material.PolylineTrailLinkSource = " czm_material czm_getMaterial(czm_materialInput materialInput)\n\
                                                    {\n\
                                                        czm_material material = czm_getDefaultMaterial(materialInput);\n\
                                                        vec2 st = materialInput.st;\n\
                                                        vec4 colorImage = texture(image, vec2(fract(st.s - time), st.t));\n\
                                                        material.alpha = colorImage.a * color.a;\n\
                                                        material.diffuse = (colorImage.rgb+color.rgb)/2.0;\n\
                                                        return material;\n\
                                                    }";

        Cesium.Material._materialCache.addMaterial(Cesium.Material.PolylineTrailLinkType, {
            fabric: {
                type: Cesium.Material.PolylineTrailLinkType,
                uniforms: {
                    color: new Cesium.Color(0.0, 0.0, 1.0, 0.5),
                    image: Cesium.Material.PolylineTrailLinkImage,
                    time: -20
                },
                source: Cesium.Material.PolylineTrailLinkSource
            },
            translucent: function (material) {
                return true;
            }
        });
    }

    /**
     * 创建线
     * @param {*} positions 位置
     * @param {*} width 宽度
     * @param {*} color 颜色
     * @param {*} duration 持续时间 毫秒
     * @param {*} d 
     * @returns 
     */
    createPolylineTrailLink(positions, width = 5, color = Cesium.Color.WHITE, duration = 3000, d = 1) {
        let entity = this.viewer.entities.add({
            name: 'PolylineTrail',
            polygon: {
                hierarchy: positions,
                width: width,
                material: new Cesium.PolylineTrailLinkMaterialProperty(color, duration, d)
            }
        });
        return entity;
    }

}
